std::experimental::ranges::find,std::experimental::ranges::find_if,std::experimental::ranges::find_if_not (3) - Linux Manuals

std::experimental::ranges::find,std::experimental::ranges::find_if,std::experimental::ranges::find_if_not: std::experimental::ranges::find,std::experimental::ranges::find_if,std::experimental::ranges::find_if_not

NAME

std::experimental::ranges::find,std::experimental::ranges::find_if,std::experimental::ranges::find_if_not - std::experimental::ranges::find,std::experimental::ranges::find_if,std::experimental::ranges::find_if_not

Synopsis

Defined in header <experimental/ranges/algorithm>
template< InputIterator I, Sentinel<I> S, class T, class Proj = ranges::identity >
requires IndirectRelation<ranges::equal_to<>, projected<I, Proj>, const T*> (1) (ranges TS)
I find(I first, S last, const T& value, Proj proj = Proj{});
template< InputRange R, class T, class Proj = ranges::identity >
requires IndirectRelation<ranges::equal_to<>, (2) (ranges TS)
projected<ranges::iterator_t<R>, Proj>, const T*>
ranges::safe_iterator_t<R> find(R&& r, const T& value, Proj proj = Proj{});
template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred > (3) (ranges TS)
I find_if(I first, S last, Pred pred, Proj proj = Proj{});
template< InputRange R, class Proj = ranges::identity,
IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred > (4) (ranges TS)
ranges::safe_iterator_t<R> find_if(R&& r, Pred pred, Proj proj = Proj{});
template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred > (5) (ranges TS)
I find_if_not(I first, S last, Pred pred, Proj proj = Proj{});
template< InputRange R, class Proj = ranges::identity,
IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred > (6) (ranges TS)
ranges::safe_iterator_t<R> find_if_not(R&& r, Pred pred, Proj proj = Proj{});

Returns the first element in the range [first, last) that satisfies specific criteria:
1) find searches for an element whose projected value is equal to value (i.e., value == ranges::invoke(proj, *i)).
3) find_if searches for an element for whose projected value predicate p returns true (i.e., ranges::invoke(pred, ranges::invoke(proj, *i))) is true).
5) find_if_not searches for an element for whose projected value predicate q returns false (i.e., ranges::invoke(pred, ranges::invoke(proj, *i))) is false).
2,4,6) Same as (1,3,5), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.
Notwithstanding the declarations depicted above, the actual number and order of template parameters for algorithm declarations is unspecified. Thus, if explicit template arguments are used when calling an algorithm, the program is probably non-portable.

Parameters

first, last - the range of elements to examine
r - the range of elements to examine
value - value to compare the projected elements to
pred - predicate to apply to the projected elements
proj - projection to apply to the elements

Return value

Iterator to the first element satisfying the condition. If no such element is found, returns an iterator that compares equal to last.

Complexity

At most last - first applications of the predicate and projection.

Possible implementation

First version

  template< InputIterator I, Sentinel<I> S, class T, class Proj = ranges::identity >
    requires IndirectRelation<ranges::equal_to<>, projected<I, Proj>, const T*>
  I find(I first, S last, const T& value, Proj proj = Proj{})
  {
      for (; first != last; ++first) {
          if (ranges::invoke(proj, *first) == value) break;
      }
      return first;
  }

Second version

  template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
            IndirectUnaryPredicate<projected<I, Proj>> Pred >
  I find_if(I first, S last, Pred pred, Proj proj = Proj{})
  {
      for (; first != last; ++first) {
          if (ranges::invoke(pred, ranges::invoke(proj, *first))) break;
      }
      return first;
  }

Third version

  template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
            IndirectUnaryPredicate<projected<I, Proj>> Pred >
  I find_if_not(I first, S last, Pred pred, Proj proj = Proj{})
  {
      for (; first != last; ++first) {
          if (!ranges::invoke(pred, ranges::invoke(proj, *first))) break;
      }
      return first;
  }

Example

 This section is incomplete
 Reason: no example